How do you automatically map "params" onto an object?

Rails
1

Disclaimer: Ruby/RoR nuby

How do I automatically map my “params” object onto a model object from
within my controller?

Thanks,
Jason

2

Pretty nubish here too.
If you look at scaffold methods, it will give you a hint. ActiveRecord
objects can be mapped to a hash, and your params is just a hash, so if
your params has within it a ‘user’ key containing a hash with
‘username’, ‘password’, ‘phone’, etc, you can do
User.new(params[:user]), which is the same as doing
User.new(:username => ‘billj’, :password => ‘billrules’, :phone =>
‘123-456-7890’)
Thanks,
Jason

3

I was hoping to use a generic approach and not have to specific each
field [column].

Does any body know of a generic way to do this and handle “extra”
parms?

Thanks,
Jason

4

The main trick here is to match the params keys to the field names in
your database.

For example:

–DB
create table comments
title varchar(50)
text varchar(255)
end

–view
form_tag :controller => ‘comments’, :action => ‘add’
text_field(‘comment’, ‘title’)
text_area(‘comment’, ‘text’)
submit_tag “Add Comment”
end

–Comments Controller
def add
Comment.create(params[:comment])
end

5

On 12/11/06, Jason Vogel [email protected] wrote:

Disclaimer: Ruby/RoR nuby

How do I automatically map my “params” object onto a model object from
within my controller?

The answer lies within the scaffold code, have you tried generating a
scaffold for a model and looked at it?

–
_Deirdre http://deirdre.net/

6

I think I understand:

If the params hash has keys that do not match the database fields you
will end up with “method not found” type errors.

I have been looking for a neat way around this issue. I suspect the
answer will come from the “method_missing” hook, but this may cause
genuine errors to fail silently…

7

User.new(params[:user]), which is the same as doing
User.new(:username => ‘billj’, :password => ‘billrules’, :phone =>
‘123-456-7890’)

Jason just needed one more sentence to explain this. The point is that
params[:user] is really:

PARAMS
–USER
–username => ‘billj’
password => ‘billrules’
phone => ‘123-456-7890’

So params[:user] returns another hash. To call them individually you
have to say:

params[:user][:username]
params[:user][:password]
params[:user][:phone]

So by constructing the proper fields text_field(‘user’, ‘email’)
becomes:

params[:user][:email]

and so forth. By having a model object ready to accept these hash=>key
pairs you can suck them all in at once with:

@user = User.new(params[:user])

In this case your model would need to be:

User
username
password
phone
email

8

Doh! of course!

It never occurred to me to put all the model specific values into their
own array on the form, which solves the “method_missing” errors.

9

On 12/11/06, askegg [email protected] wrote:

I think I understand:

If the params hash has keys that do not match the database fields you
will end up with “method not found” type errors.

I have been looking for a neat way around this issue.

In your model:

attr_accessor :foo

–
_Deirdre http://deirdre.net/